The present invention relates to a method and apparatus for producing a disc record with a relatively large diameter center hole, and particularly to a method and apparatus for molding-in the center hole in the disc record.
It has been found desirable to provide an information record with a relatively large diameter center hole, i.e., about 1.5 inches (3.8 cm) in diameter. Heretofore small diameter center holes on the order of 0.25 inch (0.6 cm) in diameter, have been molded-in in disc records as shown by U.S. Pat. No. 3,662,051 to L. C. Harlon et al, issued May 9, 1972 entitled "Automatic Record Molding Apparatus and Method". However, large diameter holes are more difficult to mold-in since considerably more materials must be displaced during molding.
It is also possible to punch the record center hole after the record has been molded. This approach, however, is undesirable from a cost viewpoint since it requires additional equipment and process steps. This approach is also undesirable where the record center hole is relatively large, and where the record is relatively brittle. A further disadvantage of this technique is that it generates debris which may remain on the record and disrupt the playback of the record.
Another record manufacturing approach may utilize an in-mold punching operation in the manner described in U.S. Pat. No. 3,989,436, issued to McNeely et al on Nov. 2, 1976. However, where the record is relatively brittle, it is difficult to punch out relatively large diameter center holes without damaging the record surface.